I introduced this build failure in golang.org/cl/9302 but failed to
notice due to the other failures on the dashboard.

Change-Id: I84bf00f664ba572c1ca722e0136d8a2cf21613ca
Reviewed-on: https://go-review.googlesource.com/9363Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>